The present invention relates to a laser surveying device which carry out distance measurement by projecting a laser beam to an object to be measured and receiving a reflected light from the object to be measured.
Conventionally, a laser surveying device has been known, which projects a laser beam in pulses to an object to be measured, receives a reflection light, from the object to be measured by a photodetection element and carries out distance measurement per each pulse.
Normally, in a case where distance measurement is carried out by a pulsed distance measuring light, the distance measurement is carried out by a TOF (Time of Flight) method which carry out distance measurement by emitting the next pulsed distance measuring light after receiving a pulsed distance measuring light reflected from the object to be measured.
In a case where distance measurement is carried out on an object to be measured as located at a distant place such as a bridge, a dam, etc. by the TOF method, it is desirable to emit a pulsed distance measuring light with high peak power and to carry out distance measurement so that a reflected pulsed distance measuring light having a measurable intensity can be received. On the contrary, in a case where distance measurement is carried out on an object to be measured is at a near distance, e.g. in a room or the like, it is desirable to emit a pulsed distance measuring light with a high repetition frequency and to carry out distance measurement so that measurement with high density can be carried out. In this case, there is no need to use a pulsed distance measuring light with high peak power.
As described above, in the distance measurement by the TOE method, the peak power of the pulsed distance measuring light differs according to the distance to the object to be measured. However, in the conventional type laser surveying device, the peak power and the repetition frequency of the pulsed distance measuring light as projected to the object to be measured are fixed. As a result, it has been necessary to use different types of laser surveying device in a case where an object to be measured is at near distance and in a case where an object to be measured is at long distance.